Zirconium containing composition and process of making the same



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' To all concern:

citiaen. of the United States, residing at Cleveland, in'thecounty of Guyahoga and 4 5 State of Ohio, have invented certain new and useful'Improvements in Zirconium Contain-v ing. Compositions and Processes of Making. the Same,-of which the following is a .speci-'. .fication.- 1. This invention relates ,toimprovement's in I processes oftreatin crude materials con taining zirconium silicate for the production of acomposition suitable, for use as an opaci-'.'

g agent in the enamel industry, and 1 for-fother purposes. l I Numerous -attempts havebeen made .to

produce a; satisfactory..-substitute for stannic' oxid, which is new regarded as the standardopacifier'Tfor highfgrade enamels, and

'2 ithasbeen'sho'wn that Zirconium compounds I have'possibilities in this. connection Zirconium'Po xid is relatively satisfactory-, butresidualsludge, prefera itshigh-costj precludes itsextensive .use. In' my application Ser.- No. 456,742,"filed and efiective zirconium opacifier may} be pre{. pared by special. treatment of: crude zir- ,1 coniumsilicate, occurring ;in nature as the mineral zircon. The presentinvention' com- 0 'vprisesi improvements in the process di s-' "closedfin said application.

The print al method. which I have outs lined inv app'ication- Ser; 1N6. ,4 56,74=2,'may 4 1 be; summarizedfasj follows: Zircon-isseparated 'froin associated minerals. and is sub-- "'jected to a, wet-milling operation until it .ap-

. proaches a colloidal condition. It is next.- treated withan acid solution: to dissolve iron; and otherimpuriti'es, after which 'it is thoroughly" washed. and dried. "The purified .material is preferablycalcinedat a itemperat.ure of.-aboutf1$)00 C. The'resulting j roduct givesanenamel'of'good-whiteness, but ofonly fair opacity; and insufiicient 1uster-.' These deficiencies are .corre'cted'by using the purified zirconium silicate in connection w th -materials producing. intense opacity and highluster, such as tin oxid.*

s' process, asdescribed herein, I am.

v able to obtain from 'ferruginous zirconium Silicate a material capableof independent use as an opacifier. Enamels prepared with no other opacifier than the product of my {than when dry like. After the'acid. treatment, the silicate is thoroughly washed. Preferably it is firstplaced in water, which is brought to the boil- 2 The-solution is then decanted, and the sludge subjected to repeated wash- Application filed au ust dieenseria i fe'. 491,soo.' k

-. process arecharacteriz'edThy satisfactory Be it known that I, HUGH S. COOPER, a

whiteness, opacity, and brillianey.

The zircon is first separated in anysu itable way-from associatedminerals, unless these are, capable of: imparting desirable properties to the finished product." In the present method, either wet or dry milling may-- be used to break down the crystalline structure of. the silicate. '"-.I prefer, however,- to subject the. material to a wet-milling operation, becausewhen ground in this wayit 'is -more' readily susceptible to theacid and 'allrali' treatments to be described, and

the coveringpower of the productiis better (grinding is'adopte'd. Q The operation shoul -be .continued 'j'until the colloidal condition is approached; severaldays may be required for the completion of this step-of the'proce'ss. i

The-waryiinely subdivided material is drawn off from thejmill, allowed to settle,

and thesupernatant liglld decanted. The I l'y without drying, ls treated with concentrated sulfuric acid in the proportion. of 2 or 3--'parts by. weight of 93% acid' to 1 part of wet'silicate. --Heat is applied and the mixture evap'oratedfdownto a pasty-condition," or. to dryness. Theiron and other detrimental impurities in the mineral are converted into solublesul-j fates. byf -.this; treatmentI The zirconium silicate itself is'not -chemically*changed to any considerable extent, but 'it' is n evertheles's modified in ahighl-y advantageous mani 'ner. The transformation may bedue to a muonaroms- 9011+ changein the physical'condition of the silicate.particl es,' or to',a combined chemical. andplhysical action. Whether or not-theseare t e' causes, I-have found that theresult i s-:the production of an 'opacifierflfhaving much more satisfactory" characteristics than when prior methods of preparation are used. The benefit to be derived from this treat- .ment with regard :to' increased covering power and other desirable propertiesis sufiicient to justify its'use even whenit is not.)

necessary .to-remove iron compounds .or the ing point.

ing and decantation until all traces of solucate. I have found that an .iron content of from 0.4% to 0.75% causes. a yellow tinge in the finished enamel, and. that more than 1.0% iron will render the silicate unfit for most enameling' purposes. The process described reduces the iron to an amount substantially less than the percentages stated.

' The'productat this stage is free from discoloration and highly voluminous.

It may in some cases be used as an opacifier without further'treatment.

-I prefer, however, to subject it to calcination, as this resultsin improved brilliancy and opaquing qualities. The temperature of calcination may be about 1000 C. and the time of heating may be, forexample, two

hours. The silicate suffers no apprecia le decomposition under these conditions,

The zirconium silicate opacifier prepared as described herein produces enamels equal in all respects .to those in which tin oxid is the clouding agent. It is necessary, however, to use about-one-third more of the (silicate than of tin-oxid in order to secure equivalent results, In gen'eraI the amounts of silicate will range from 6% to 15% of the total weight of the'enamel composition. The proportions may vary between these and even wider according to the degree of opacity desired or other conditions of the particularwork in hand.

I have discovered further, (that? the high percentage of combined silica in the prepared zirconium silicate is largely'nesponsible forthe deficiency of that compoundin opaquing capacity, as compared with an equal weight of tin' oxid. In some cases, therefore, I prefer to subject the silicate, containing usually around'33% of combined silica, to a treatment with alkali and in 'this'way reduce the silica content to the desired extent. 'When the silica is lowered to 10 to 15%, the re-- sulting product is approximately the opacir fying equivalent, weight for weight, of tin oxid. he percentage may'vary between 7 and 25 without substantial departure from.

the desired result.

The alkali treatment is carried out as follows: Zirconium silicate, preferably sub jected to the action of concentrated sulfuric acid,'washed, and dried, as described above, is added to about2 times its weight of molten alkali metal hydroxid at a temperature of approximately 400 C. The silicate is advantageously1 added to the alkali in small. batches, as the eat of reaction causes a rapid rise of temperature and'considerable ebullition. When all of the-material has been added and actioh-ceases,-heating is continued mass 'shows signs of solidifying; 7

the solids are washed several-times by addii tion of water and decantation. The greater 7 portion ofthe alkali, alkali metal silicate" and other soluble salts, is removed: in this way. When the liquor shows signs of turbidity the solution isboiled for several hours to break up the alkali metal zircpnate formed during the fusion. Residual alkali is removed by thorough washing, preferably through a filter press. The removal of alkali is preferably as complete as possible, though when present in amounts less than 2% it is not' particularly objectionable. material, after final drying and calcining, contains about'12'% of silica. -It is the full equivalent of stannic oxid with respect to luster, opacity and freedom fromdiscoloration when used in enamel compositions.

The reduction of the silica content may be regulated by adjustingthe amountof al- The 7 kali and time of fusion. For example, with a weight of alkali only twice that'of the zircomum silicate and a somewhat shorter period. of reaction, the residual silica amounts'to about 23%. The preferred alkali is sodium hydroxid, but the other alkali metal hydroxids and alkali metal carbonates may be used. The fusion process described is not limited to use with zircon. treated according to the process herein 'set forth. The fine subdivision of the wet-milled and acid treated silicate, however, renders it especially suited for the subsequent alkali treatment. Compositions containing. any desired proportion of silica might, of course,

be prepared by mixing zirconium oxid with the silicate. uch compositions however, do not give asgood results as those prepared by ,in the latter a lower silicate of zirconium 4 chemical removal of. silica, possibly because 7 is present, rather than a mechanical .mix-

ture of oxid andsilicate.

' A number of valuable-clouding agents,

such as compounds of cerium, thorium, and titanium, are frequently found associate with zircon. The silicate prepared accdrding to the present process does not require their presence to enhance its opacifying qualities, but in some cases the associated substances may be retained without disadvantage. ing the minerals, the process as. descrlbed above maybe followed.

In using. zirconiumv silicate with undi'minished silica content as an opacifier, the fus- Omitting the step of'segregatible enamel components, preferably Without the opacifier, are melted and tapped off .into

water in theusual way. The frit so produced, 'with the proper amount of dry silicate', is subjected to wet-milling for several prior practice with zirconium oxid. The resulting product is preferably aged for several days, as this tends to produce a better color. When alkali treated silicate is used, it may be added as just described, or near the end of the milling process. Enamel compositions prepared as described may be ap-.

plied in ways well'understood in the art.

The product claimed herein is not limited to use as an enamel opacifier. It may be advantageously used also as a paint pigment or rubber filler, and for other purposes.

I claim:

1. Process of treating zirconium silicate,

' which comprises wet-milling the silicate to a condition of extreme fineness, reacting upon the milled material with concentrated sulphuric acid, and removing residual acid and substancesrendered soluble thereby.-

2. Process of treating naturally occurring zirconium silicate, which comprises wetmilling the silicate to a condition of extreme fineness, treating the milled material with concentrated sulphuric acid, and then washing, drying, and calcining the material.

3. Process of treating naturally occurring zirconium silicate for use as an enamel opacifier, which comprises milling the silicate to finely divided condition and treating the miled material with concentrated sulfuric aci 4. Process according to claim 3, in which the mixture of silicate and acid is subjected to heat sufficient to evaporate the mixture at least to a pasty consistency.

5. Process according to claim 4, in which the evaporation is continued to dryness- 6. Process of treating naturally occurring zirconium silicate, which comprises wetmilling the silicate to a condition of extreme fineness, acting upon the milled material with concentrated sulfuric acid, under conditions such as to obtain a substantially dry product, and washing, drying and calcining the product.

7. Process of treating zirconium'silicate which comprises milling the silicate to a condition of extreme fineness, reacting upon the milled material with concentrated sulphuric acid, removing water soluble substances,

subjecting the material to the action of alkali at high temperature, and removing excess alkali.

8. Process according to claim 7 in which the alkali treatmentv is a fusion with alkali metal hydroxid at approximately 4L00 C.

9. Process according to claim 8, in which one part of silicate is added to about 2?; parts of alkali.

10. Process of enhancing the opacifying quality of zirconium silicate, comprising reducing the silica content of said compound to between 7 and 25%, by a treatment with alkali and subsequent removal of water soluble substances.

11. Process of enhancing the opacifying quality of zirconium silicate, comprising fusing said compound with approximately 21} times its weight of alkali metal hydroxid, and removing water soluble substances from the fusion product;

\ 12. Process of preparing an enamel composition, comprising finely dividing and purifying a naturally occurring zirconium silicate, preparing a frit from fusible enamel constituents, and reducing said frit to finely divided condition by a wet-milling operation, said silicate being commingled with the frit prior to said operation.

13. Zirconium silicate such as may be obthan 0.75% iron.

15. As an enamel opacifier, substantially pure, finely divided zirconium silicate having physical and chemical characteristics due to contact with concentrated sulfuric acid, such characteristics enabling the silicateto impart highluster and opacity to enamels.

16. As an enamel opacifier, the zirconium tained by reacting upon the naturally occursilicate with concentrated sulfuric containing product resulting from the reduction of the silica content of zirconium silicate to 7 to 25%. y

17. Zirconium silicate in which the silica 7 content has been reduced by treatment with alkali to? to 25%, said silicate containing less than 1% iron and less than 2% alkali.-

18. Zirconium silicate in which the silica content has been reduced by treatment with alkali to 10 to 15%, said silicate containing 

